After making his major league debut in September of 2010 with the Atlanta Braves, Freeman was the Braves' starting first baseman on opening day on March 31, 2011. It was the third straight year that the Braves had put a rookie in their line-up on opening day, following Jordan Schafer in 2009 and Jason Heyward in 2010; the two were also making their major league debuts on the occasion, contrary to Freeman, and both hit home runs to start off their major league careers. In contrast, Freeman went hitless in three at-bats against the Washington Nationals'Livan Hernandez. However, he quickly settled into his starting role and was a key part of the Braves' offense as they kept pace within a few games of the Philadelphia Phillies and of first place in the NL East. He was named the National league's Rookie of the month for July, when he hit .362/.433/.600 in 27 games; he hit six homers and drove in 18 runs while scoring 17. He had his first multi-homer game on July 4th facing the Colorado Rockies at Turner Field. He finished the season with a batting line of .282/.346/.448 in 157 games, with 21 homers and 76 RBI, although he did not make the 2011 Topps All-Star Rookie Team, losing out to Mark Trumbo of the Los Angeles Angels of Anaheim.

In 2012, Freeman's batting average fell in comparison to his rookie season, although the rest of his numbers stood and he continued as the Braves' regular first baseman. He played 147 games, hitting .259 but his OBP was at .340 and his slugging percentage at .456, so his OPS+ was almost unchanged 113 compared to 116 the previous season, He hit 23 homers and drove in 93 runs as the Braves won one of two wild card berths in the National League. He went 3 for 4 with a double and a walk as Atlanta's best hitter in its loss to the St. Louis Cardinals in the Wild Card Game. Back as the starter at first base for the Braves in 2013, he suffered the first injury of his career in early April, a strained oblique muscle which forced him to go on the disabled list. He was not happy at the turn of events, complaining that the injury was only "a two-day thing" and that he would now need to miss 15 games because of his team's decision. However, in spite of the time missed, he was the Braves' most consistent hitter during the first half, and while he was not originally picked for the All-Star team, he won the "Final Man Vote" against four other players to be added to the squad. What made it more remarkable is that he beat out rookie Yasiel Puig, who had had a sensational debut and had been the most talked-about player in the majors for the month that preceded the vote, while Freeman had produced steadily but quietly. He was hitting .307 at the time of his selection, and although he had hit only 9 homers, he had 18 doubles, 49 runs scored and 37 RBI, all three totals putting him on a pace to set new personal bests. He celebrated by driving in four runs in a 6-5 win over the Cincinnati Reds on the day of his election, July 11th. However, he suffered a jammed thumb in the last game before the break, on July 13th, and had to give way to teammate Brian McCann on the National League squad. He finished the year with an excellent batting line of .319/.396/.501 in 147 games, good for an OPS+ of 144. He had 23 homers and 109 RBIs, then went 5 for 16 with a double and 4 runs scored as the Braves lost to the Los Angeles Dodgers in the NLDS. He was 5th in voting for the 2013 NL MVP behind Andrew McCutchen, Paul Goldschmidt, Yadier Molina and Matt Carpenter.

Freeman was eligible for arbitration for the first time before the 2014 season but the Braves preempted a decision by inking him to the largest deal in franchise history on February 5th, an eight-year contract worth $135 million.